(1) Field of the Invention
The present invention relates to an opto-thermal conversion recording apparatus which converts light corresponding to image information into heat to melt thermo-melting ink so that the image information is recorded on a sheet of recording paper.
(2) Description of the Prior Art
Conventionally, as an image recording system, a thermal transfer recording system has been known in which as shown in FIG. 7, an ink ribbon 3 that is composed of a base film 2 and thermo-melting ink 1 applied on a surface thereof is heated by a thermal head 4 so that the thermo-melting ink 1 on the ink ribbon 3 is melted and transferred to a sheet of recording paper 5.
An ink film used in this thermal transfer recording system is expensive and it is very difficult to recycle the ink film which has been once used for a thermal transfer process. Therefore, even if the thermal transfer recording apparatus itself is inexpensive, the running cost due to the consumption of ink films is high. Since the number of recording pixels and the resolution are determined by the number and density of the heat generating elements on the thermal head, development of the head to a higher resolution or provision of a line head increases the cost. Moreover, since the recording trace of the ink which has not been thermally transferred remains as it is on the ink film, this results in poor security protection.
Japanese Patent Application Laid-Open Hei 4 No.255,392 proposes an opto-thermal conversion recording system which uses a heat generating drum 11 having a light transmissive hollow base 6 with a lamination of a transparent electrode layer 7, a photoconductive layer 8, a conductive layer 9 and a thermo-melting ink layer 10 formed thereon in this sequential order, as shown in FIG. 8. In this configuration, with a voltage applied between the transparent electrode layer 7 and the conductive layer 9, rotatable heat generating drum 11 is irradiated with light which contains image information from the inner portion thereof. This causes the photoconductive layer 8 at the illuminated portion thereof to become conductive so that heat is generated by the Joule effect and the ink in thermo-melting ink layer 10 melts and transfers to the recording sheet. Then, ink is supplied to the portion where ink has been transferred, to restore the thermo-melting ink layer to its original state. In this way, this system realizes continuous recording.
However, the opto-thermal conversion recording system disclosed in Japanese Patent Application Laid-Open Hei 4 No.255,392 suffers from the following problems:
1) It is very difficult to create a thermo-melting ink layer of a uniform thickness on a drum; PA0 2) Since ink is transferred to the recording paper whilst the thermo-melting ink layer and the recording paper are being pressurized between the heat generating drum and a platen roll, the ink could adhere to areas other than the recording portions due to friction or the like, polluting the recording sheet; and PA0 3) Since the recorded quality of the pixel area is determined in accordance with an area of the illuminated portions, due to heat diffusion it is impossible to create fine or micro recording pixels which are required for high resolution and high gradation image forming.